This is the 3532nd most frequent Arabic word.
وحده
"By himself," "alone," or "only him."
Here, 'وحده' is used to indicate that the person was alone, without anyone else present.
كان يجلس في الغرفة وحده.
He was sitting in the room alone.
In this context, 'وحده' emphasizes exclusivity, stating that the success mentioned by itself is insufficient.
هذا النجاح وحده لا يكفي.
This success alone is not enough.
Here, 'وحده' highlights the specific subject 'the solution' as requiring time, without including other factors.